Fir filter help me to convert into c++

[Darwin1234]

Hi guys,

I read this thread because i believe the guys here will help me );-)
i am trying to make a flanger effects.
**broken link removed** or you can check here.
https://sound.eti.pg.gda.pl/student/eim/synteza/adamx/eindex.html

and according to the site flanger should be like this

The difference equation is y=x+ax(n-D), where, for example D=d/2(1-cos(2pFn)), F - deviation speed (about 1 Hz), d - deviation rate.
The modulation of delay time causes dynamic changes in dips and peaks position. Additional effect is time stretching of audio signal. The time delay varies between 1 and 5 ms. Alike echo there is FIR and IIR version.

so now my question. how can i convert the formula to c++?
y=x+ax(n-D), where, for example D=d/2(1-cos(2pFn)),

everyone?


thanks in advance!

 

[FvM]

Try to understand Pic.2 in the article and consider how it can be implemented in a processor. Hint: the variable delay line is usually realized as a ring buffer. Start with a fixed delay y=x+ax(n-b) (similar to an echo) and if it works design the modulation.

 

[Darwin1234]

Hi FvM,

thank you for the information, i know about the circullar buffer or ring buffer. i have code it like this

check my code.

cbuffer[echooffset]=input*0.5;// original *  ( amount of original )
            if (echooffset++>=ECHO-1)echooffset=0;
            ouput+=cbuffer[echooffsetplay]*0.4;// amount to mix into dry
            if (echooffsetplay++>=ECHO-1)echooffsetplay=0;
}

but i want to know how to implement the LFO. which is implement by flanger.

=x+ax(n-D), where, for example D=d/2(1-cos(2pFn)), F - deviation speed (about 1 Hz), d - deviation rate.

 

[FvM]

Use a sine table.

 

[Darwin1234]

Hi sorry for late response. i would like to know how we can implement the sinewave LFO on my codes.

cbuffer[echooffset]=input*0.5;// original * ( amount of original )
if (echooffset++>=ECHO-1)echooffset=0;
ouput+=cbuffer[echooffsetplay]*0.4;// amount to mix into dry
if (echooffsetplay++>=ECHO-1)echooffsetplay=0;
}

where to put the sinewave?